1. Field of the Invention
This invention relates to a novel process for preparing hydroxy aromatic carboxylic acids or the corresponding ester derivatives thereof. More particularly, this invention relates to a novel process for the preparation of hydroxy aromatic carboxylic acids such as 6-hydroxy-2-naphthoic acid by the carbonylation of a hydroxy aromatic halide.
2. Description of the Prior Art
Hydroxy aromatic carboxylic acids and their application in various technological areas such as dyes and pigments are well known in the art. The technological applications of hydroxy aromatic acids are also continuing to expand. An example of one hydroxy carboxylic acid in particular whose technological applicability has resulted in an increased demand for the compound is 6-hydroxy-2-naphthoic acid. The increased demand for such hydroxy aromatic acids has also intensified the search for more commercially acceptable methods of synthesizing said compounds.
The formation of aromatic carboxylic acids or functional derivatives thereof by reactions involving the carbonylation of aromatic systems is well recognized in the art. One type of reaction between an aromatic system and carbon monoxide involves the insertion of a carbonyl group into a molecule between the aromatic moiety and a functional moiety attached thereto. For example, U.S. Pat. No. 3,452,090 discloses a process for the production of aroyl halides in which an aryl halide is reacted with carbon monoxide in the presence of a platinum, palladium, ruthenium, rhodium, osmium, or iridium catalyst and an inert solvent. The reaction takes place at the site of the halogen resulting in the insertion of a carboxyl group into the molecule to thus form the aroyl halide. The aforegoing patent discloses that substituents other than the halogen groups can be attached to the aromatic system as long as the substituents are inert and are not affected by the reaction. Examples of such inert substituents are the alkyl groups and nitro groups. Hydroxy groups are not disclosed, however, as possible substituents.
A. Schoenberg et al, in the Journal of Organic Chemistry, Volume 39, pp. 3318-3326 (1974), disclose the reaction of aryl and vinylic bromides and iodides with carbon monoxide and an alcohol in the presence of a tertiary amine and a catalytic amount of a palladium-triphenylphosphine complex to form esters. With respect to substituent effects, the carbonylation was reported to proceed most rapidly with electron withdrawing substituents on the aromatic ring, in contradistinction to electron donating substituents which produced appreciably decreased reaction rates. As well, the brominated naphthalenes were reported as being significantly less reactive than other aryl bromides. Based upon said reports the carbonylation of a hydroxy aromatic halide, and in particular a brominated naphthol, to obtain a hydroxy aromatic acid such as 6-hydroxy-2-naphthoic acid, or the corresponding ester thereof, would appear to have little chance, if any, of success. Indeed, no attempt to carbonylate a hydroxy aryl bromide or iodide was reported.
Stille, et al, in the Journal of Organic Chemistry, Volume 40, pp. 532-534 (1975), and Hidai et al, in the Bulletin of the Chemical Society of Japan, Volume 48, pp. 2075-2077 (1977), disclose the reaction of organic halides in the presence of an alcohol and palladium complex catalyst. However, the reaction of hydroxy organic halides is not reported.
U.S. Pat. Nos. 3,769,324 and 3,769,326 disclose the carbonylation of hydroxy aromatic compounds. However, the carbonylation reaction takes place at the site of the hydroxy group. More specifically, carboxylic acids and their esters can be obtained by reacting aromatic alcohols, and the ester, ether, and halide derivatives thereof, with carbon monoxide in the presence of an iridium, osmium or ruthenium catalyst system. The reaction can take place under a broad range of temperature and pressure conditions, e.g., a temperature in the range of 50.degree.-300.degree. C. and a carbon monoxide partial pressure in the range of 1-15,000 psi, with the reaction involving the insertion of a carbonyl between the hydroxy, ester, ether or halide moiety and the remainder of the molecule. For example, benzoic acid is prepared from a phenol feedstock and phenyl acetic acid from a benzyl alcohol feedstock.
U.S. Pat. No. 2,565,463 discloses a process for the carbonylation of organic halides wherein an aryl halide is reacted with carbon monoxide in the presence of a carboxylic acid modifier, e.g., an alkanoic acid such as acetic, propionic, succinic, adipic, stearic or palmitic acid. The presence of the carboxylic acid modifier results in the formation of an anhydride product which can then be readily converted to the acid upon the subsequent addition of water.
U.S. Pat. No. 3,009,951 discloses a process for carbonylating an aryl halide to produce carboxylic acids or their corresponding esters and salts. The ester of an aromatic carboxylic acid is obtained upon conducting the reaction in the presence of an alcohol.
U.S. Pat. No. 4,016,194 discloses the preparation of phenylenediacetate diesters by the catalytic insertion of carbon monoxide into the carbon-chlorine bonds of .alpha., .alpha.'-dichloroxylenes by the reaction of said xylenes in the presence of alcohols.
Two-phase reaction mediums have also been employed successfully in preparing carboxylic acids via the carbonylation of an aromatic system. For example, U.S. Pat. No. 3,034,004, discloses the reaction of an organic halide with carbon monoxide with said reaction being conducted in an organic/aqueous biphase system.
U.S. Pat. No. 3,700,729, discloses reacting an organic aromatic compound, which can be a phenol or naphthol, with carbon monoxide in the presence of a substantially anhydrous organic liquid reaction medium which contains a catalyst and is inert to said reactants and catalyst. However, the reaction proceeds purely as an oxidation reaction to thus produce an oxidatively carbonylated aromatic compound which can be subsequently hydrolyzed to form the aromatic acid. No insertion of CO per se is involved.
Although the prior art has recognized, as evidenced by the aforementioned patents, many different processes involving various reactants, reaction media, catalysts and reaction parameters for the formation of aromatic carboxylic acids by carbonylated an aromatic system with insertion of a carbonyl group, such a reaction has not been employed to produce hydroxy aromatic carboxylic acids, and more particularly, hydroxy naphthoic acids. Instead, hydroxy aromatic carboxylic acids such as the naphthoic acids, and in particular, 6-hydroxy-2-naphthoic acid, have typically been prepared by other methods. These methods, however, due to the disadvantages associated with each, has limited the commercial application of hydroxy aromatic carboxylic acids.
For instance, one of the first reactions to form the specific hydroxy aromatic carboxylic acid, 6-hydroxy-2-naphthoic acid, was reported in 1923 by Butler and Royle in the Journal of the Chemical Society, Volume 123, p. 1649. The synthesis involved initially producing 2-cyano-6-naphthalene sulfonic acid by diazotizing Bronners' Acid (2-amino-6-naphthalene sulfonic acid) with sodium nitrite in the presence of hydrochloric acid and then treating with cuprous cyanide in accordance with the well known Sandmeyer Reaction. The 2-cyano-6-naphthalene sulfonic acid is then hydrolyzed with potassium hydroxide to the potassium salt of 2-carboxy-6-naphthalene sulfonic acid, which is then fused with potassium hydroxide at 260.degree.-280.degree. C., or treated with a 25% aqueous solution of potassium hydroxide at 260.degree. C. in 30 atmospheres of pressure, to thereby produce the 6-hydroxy-2-naphthoic acid. The overall yield from the initial starting material of Bronners' Acid is about 50%, which is an attractive reaction yield for commercialization purposes. One of the disadvantages associated with the Butler et al synthesis stems from the fact that Bronners' Acid is a carcinogen and/or generally contains the potent carcinogen .beta.-naphthyl amine as an impurity. Moreover, hydrogen cyanide is evolved during the Sandmeyer Reaction. Thus, to commercialize the aforegoing process would be extremely costly due to the necessary provision of safeguards for the handling of the Bronners' Acid and the protection of the workers against the hydrogen cyanide evolution.
Another process for forming 6-hydroxy-2-naphthoic acid is a two step synthesis route discussed by Cason in the Journal of the American Chemical Society, Volume 63, page 828 (1941). In the first step of this process, potassium cyanide or potassium ferricyanide is fused with Bronners' Acid in order to replace the sulfonic acid grouping with a cyano group. The second step involves a hydrolysis of the cyano group with simultaneous replacement of the amino group with hydroxyl to thereby form the 6-hydroxy-2-naphthoic acid. Unfortunately, the yield of the 6-hydroxy-2-naphthoic acid is extremely low, which, along with the disadvantages inherent in the handling of the carbinogenic Bronners' Acid and the possibility of hydrogen cyanide evolution during the potassium cyanide or potassium ferricyanide fusion step, make the process extremely unattractive for commercial purposes.
Knowles et al reports another process for synthesizing 6-hydroxy-2-naphthoic acid in the Journal of Organic Chemistry, Volume 1, page 374 (1942). The hydroxy carboxylic acid is prepared from a starting material of 6-methoxy-2-bromonaphthalene, which is prepared from .beta.-naphthol in three steps. Once the 6-methoxy-2-bromonaphthalene is obtained, its Grignard reagent is prepared and then carbonated to provide a 50% yield of 6-methoxy-2-naphthoic acid. The 6-hydroxy-2-naphthoic acid is then obtained from the methoxy compound by cleaving the methylether with hydrobromic acid (HBr) in aqueous acetic acid. The yield of 6-hydroxy-2-naphthoic acid is about 75%.
A process for preparing 6-hydroxy-2-naphthoic acid from 6-methoxy-2-bromonaphthalene differing from that reported by Knowles et al was subsequently reported in the Journal of the American Chemical Society, Volume 65, page 234 (1943) by Anderson et al. This synthesis involves acetylating the 6-methoxy-2-bromonaphthalene in nitrobenzene with acetyl chloride in the presence of aluminum chloride to give a 50% yield of 6-methoxy-2-acetonaphthone. The acetonaphthone is then oxidized with hypobronite (NaBrO) to give a 75% yield of 6-methoxy-2-naphthoic acid, which is then demethylated with hydrobromic acid in aqueous acetic acid to produce the 6-hydroxy-2-naphthoic acid.
The Knowles et al and Anderson et al syntheses have met with limited commercial acceptance, however, due to the undesireable use of the cancer suspect agents, dimethyl sulfate and nitrobenzene, as well as the large number of reaction steps, i.e., beginning initially with a three step process to initially produce the 6-methoxy-2-bromonaphthalene and then subsequently obtaining the 6-hydroxy-2-naphthoic acid by an additional two or three steps.
Another well known procedure for synthesizing the 6-hydroxy-2-naphthoic acid is via the Kolbe-Schmidt reaction (see U.S. Pat. No. 257,815; cf. U.S. Pat. No. 1,593,816). This process involves the reaction of potassium naphtholate with carbon dioxide in the absence of a solvent at a temperature in the range of about 170.degree.-230.degree. C. for about eight hours. The product obtained is a mixture of 6-hydroxy-2-naphthoic acid and 3-hydroxy-2-naphthoic acid. It has been reported that the 6-hydroxy-2-naphthoic acid can be recovered with 28-36% yield; however, other experimental reports, such as that by E. Schwenk in Chemiker-Zeitung, Nr. 30, S297-304, (1929) and Nr. 34, S333-340 (1929), have indicated problems in obtaining the 6-hydroxy-2-naphthoic acid in the aforegoing yields via the Kolbe-Schmidt reaction.
Thus, the search has continued for a more commercially advantageous process for the production of hydroxy aromatic carboxylic acids in general, and more specifically, 6-hydroxy-2-naphthoic acid. Such a process would most desirably overcome the problems of the prior art processes, i.e., avoiding the handling of carcinogens or the production of toxic materials, employing a limited number of steps and consistently producing the desired product in a good yield. The instant invention was developed in response to this search.
Accordingly, it is an object of this invention to provide a novel process for producing hydroxy aromatic carboxylic acids via carbonylation.
Another object of this invention is to provide a process for producing hydroxy aromatic carboxylic acids wherein the handling of carcinogens is substantially avoided.
Another object of this invention is to provide a process for producing hydroxy aromatic carboxylic acids in good yields.
Another object of this invention is to provide a commercially viable and economically acceptable process for the production of hydroxy aromatic carboxylic acids wherein inexpensive starting materials are employed and a large number of reaction steps is avoided.
Another object of the present invention is to achieve regioselectivity in the synthesis of hydroxy aromatic acids.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description and the appended claims.